* { margin: 0; padding: 0; }
.box-center { width: 400px; height: 200px; background: #ccc; position: absolute;
			        margin: auto; left: 0; top: 0; right: 0; bottom: 0;  }
.quarter1 { width: 50px; height: 50px; border-radius: 0 0 50px 0; background: #ffcc00;}
.quarter2 { width: 50px; height: 50px; border-radius: 50px 0 0 0; background: #ffcc00;
            position: absolute; right: 0; bottom: 0; }

/*固定宽高div垂直居中,上下采用top/left，然后使用margin调整div一半长度*/
/*.box-center { position: absolute; top: 50%; left: 50%; margin: -100px 0 0 -200px;
              width: 400px; height: 200px; background: #cccccc; }
.quarter1 { width: 50px; height: 50px; border-radius: 0 0 50px 0; background: #ffcc00;}
.quarter2 { position: absolute; left: 350px; top: 150px; width: 50px; height: 50px;
            border-radius: 50px 0 0 0; background: #ffcc00;}*/
